Food preparation appliances such as blenders and food processors are commonly use to process foods, such as by chopping, crushing, cutting, liquefying, blending, mixing, etc. Such appliances typically have a container in which the food is loaded for processing. The container has one or more blades disposed within the container. When the container is set on a base that houses a drive motor, the drive motor is drivingly connected to the one or more blades in the container. A lid is typically placed on the top of the container to close the container during operation of the appliance.
In some blenders and food processors, the contents in the container tend to rotate about the inner volume of the container during processing. However, the contents are not always evenly mixed. Often times, for example, the contents nearest the blades may be liquefied, whereas contents located further from the blades remain intact (e.g., chunky). In order to improve the performance (i.e., improve the homogeneity of the mixed contents), at least some known containers include a series of ribs extending vertically along all or a portion of the inner sidewall of the container. These ribs may have varying sizes and shapes in cross-section, or contour as taken along the inner circumference of the container, but tend to have a symmetric incline and decline section along the circumferential contour of the inner sidewall of the container. The purpose of the ribs is to create turbulence in the contents of the container as they rotate within the container.
When the contents rotate along the inner circumference of the container sidewall, they strike the ribs and will either travel upward (e.g., vertically) along the inclined side of the rib or travel circumferentially over the rib to its declined side. The contents that travel over the rib may enter a stagnant flow region on the declined side of the rib, and in some instances the contents can remain in the stagnant region for substantially the entire duration of operation of the appliance. As such, the contents in the stagnant zone are not well processed, and the final mixture is not homogeneous. Thus, the ribs may reduce the performance and the uniformity of the final mixture contents of the blender.
The one or more blades of the appliance may also be shaped so as to impart both a rotational force and an axial force to the contents of the container during operation. For example, some blades are upwardly or downwardly angled to force the contents upward/downward as the blades strike the contents (e.g., the food), causing axial flow of the contents within the container. However, performance of the blades can vary with the speed at which the blades are rotated and the contents that are being mixed. In some instances, for example, excessive blade rotation speeds may induce cavitation within the contents being processed, or cause the contents to be forced upward and out of the top of the container. Cavitation within the contents may also cause non-uniformity in the final mixture and thus reduce the efficiency and usefulness of the appliance.
As such, a need exists for a food preparation appliance that provides improved efficiency and uniformity of the processed contents.